Projector arc-lamp.



PROJECTOR ARC LAMP APPLICATION FILED JUNE 13. 1916.

1,241,270. PatentedSept. 25, 1917.

INVENTOR.

BEN FE'H'HIB By gglox A TTORNE Bax runs, or

LAKEWOOD, OHIO, ASSIGNOB, BY MESNE ASSIGNMENTS, TO NATIONAL CABIBONCOMPANY, INCL, CORPORATION OF NEW YORK.

PROJECTOR. ABC-LAMP.

To all whom it may concern:

Be it known that I, BEN Prams, a citizen of the United States, residing at Lakewood, in the county of Cuyahoga and State of Ohio, have invented a certain new and useful Improvement in Projector Arc-Lamps, of which the following is a full, clear, and exact description.

This invention relates to projector arc lamps and is 'particularli adapted to socalledmoving icture wor In moving picture lamps it has been customary to make the negative lower somewhat smaller than the positive upper in order to have the consumption of the electrodes approximately equal and thus secure a stationary focal point. When the electrodes which consist of carbon are made in correct proportion to obtain equal burning rate, the negative is still of sufficient size to result in a cathode tip of sufiiciently large area to cause the arc to wander. In the class of work referred to it is essential that the crater remain stationary or at most change position only slowly. I have found that this requirement can be fulfilled by reducing the negative much below that required for equal burning of the electrodes, the ratio being about 4: to 1 as regards the area of cross section. However, with a negative only one fourth the size of the positive the consumption is so great as to render it impractical. To maintain the burning rate I have heavily copper coated the negative, but when the coating is made thick enough to equalize the burning rate of the two electrodes the copper spatters on the glass condenser lens which will be better understood after a general description of the projector lamp is given. The way in which these disadvantages are overcome will now to be described.

Referring to the single figure of the drawing, the large positive electrode 1 cooperates with the small negative 2 to form the crater 3 in such a way as to throw the light through the condenser lens arrangement 4: which is closely adjacent thereto.

When a single heavy copper coating 5 is employed the sheath near the negative tip melts and collects in beads 6 on the end. The molten beads have the peculiar property of spattering and flashing suddenly when the arc touches them. This causes an 5 undesirable flicker and projects molten Specification of Letters latent.

Patented Sept. 25, 1917.

Application fled June 18, 1916. Serial No. 103,405.

metal onto the glass lens where it sticks quite firmly. The copper particles must of course, be removed from the lens otherwise the transparency will be affected, and this is more or less difficult to do. For these reasons a single heavy coating of copper on the negative is unsatisfactory in practice.

I have discovered that the formation of molten beads on the negativetip may be entirely eliminated by covering the copper sheath with a second coating of nickel 7 which has been broken away at 8 in the drawing to show the inner coating 5 of copper previously referred to. The nickel and copper at the electrode end melt and do not collect in beads on the tip, but flow away from the same. Consequently the tip is always clean and there is no flashing of light and no spattering of metal on the condenser. It appears that the nickel oxidizes in greater part and forms a slag with the molten copper and copper oxid which flows away from the tip and will not form beads on account of 1ts viscosity. Metals that will exist either as molten metal or metal oxid, at the temperature in the vicinity of the negative tip will form the same sort of slag and therefore will accomplish the purpose. As further examples of such metals aluminum, lead, tin, tungsten and iron may be mentioned. Alloys of these metals also may be used for the outer coating, solder being given as one such example. I prefer to use nlckel however, as it is easy to electroplate and has other advantages.

Zinc volatilizes at a comparatively low temperature and disappears for some considerable distance below the hot tip and cannot enter into a slag-with the molten copper. Consequently it will not accomplish the desired result, as would also be true of other metals having such property.

It is preferable to apply the first coat of copper by electrolysis, which also may be the process for applying the second coat especially when the latter is nickel. The coats may be applied in other known ways, however, without departing from the spirit of the invention. For instance, with tin lead or solder the coating may be advantageously applied by dipping in the molten metal.

It is preferable to apply a plurality of coats of the two metals arranging them alternately. This gives a more uniform distribution of metal and consequently the fluxing down more readily takes lace. However two coats as first descri W111 usually produce satisfactory results th ugh a plurality of. coats are preferable as in this wa the coating approximates uniform OOmPOSI- tion. Furthermore, a plurality of coats reduces oxidation, which latter is always objectionable on account of the (poor heat and electrical conductivity of oxi s.

In practice I find it suflicient to make the nickel coat considerably thinner than the copper. An idea of the relative thicknesses may be had by stating that the electrodes have been left in the nickel plating solution about one seventh the length of time as the electrodes in the copper solution.

By means of my improvement the life of a lam trim is from two to three times as lon as when other forms of electrodes are use and the light is more satisfactory in every way.

Having described my invention what I claim is 1. In projector arc lam s, a positive electrode, a negative electr e, a heavy co per coating on the negative electrode to con uct the current and a second coating of metal adapted to form a slag with the first mentioned coatin to prevent beads of molten metal from co lecting on the tip of the negative electrode.

2. In projector arc lamps, a condensing lens, a positive electrode closely adjacent thereto, a negative electrrxle-hnvmg a cross section smaller than that necessary to maintain an ual burning rate between said electrodes, a cavy copper coating on said u tive electrode to conduct the current an to equalize the burning rate and a second coatin of metal on the first mentioned coatin a apted to prevent beads of molten meta from collecting on the tip of the negative electrode and spatterin' said condenser lens when the are springs therefrom.

3. In projector lamps, a condensin lens, a positive electrode closely adjacent thereto, a negative electrode having a cross-section smal er than that necessary to maintain an equal burning rate between said electrodes and a heavy coating of metal on said u ti ve electrmlo to conduct the current an to equalize the burning rate, said coatin consisting of a plurality of thin layers 0 cop per and nickel, alternately arranged to a proximate a uniform composition of and metals whereby molten beads of metal will not collect on the negative electrode tip but willrun down the electrode ollt of the path of the arc.

In testimony whereof, I hereunto aflix my signature.

BEN PERRIS. 

